What are the common causes of P0479?

An intermittent exhaust pressure control valve A. A loose valve A connector. A chafed valve A wire. Moisture in the valve A connector. Carbon that partly binds the valve.

Wiggle test the valve A harness while watching the signal. Inspect the valve A connector for moisture. Check the valve A wire for chafing. Clean carbon from valve A. Replace valve A if the dropouts continue. Clear the code and retest.

P0479

Exhaust Pressure Control Valve A Intermittent

System: Auxiliary emission controls (P code)
Lamp: Check Engine Light
Category: Powertrain - Auxiliary Emissions Controls

What it means

P0479 means Exhaust Pressure Control Valve A Intermittent.

Where it lives

For P0479, the description names the valve as the part involved.

Check these first

An intermittent exhaust pressure control valve A
A loose valve A connector
A chafed valve A wire
Moisture in the valve A connector
Carbon that partly binds the valve

What to do next

Wiggle test the valve A harness while watching the signal
Inspect the valve A connector for moisture
Check the valve A wire for chafing
Clean carbon from valve A
Replace valve A if the dropouts continue
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.